Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, a generator, a gearbox, a nacelle, and one or more rotor blades. The rotor blades capture kinetic energy of wind using known airfoil principles and transmit the kinetic energy in the form of rotational energy so as to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
The construction of a modern rotor blade generally includes skin or shell components, spar caps, and one or more shear webs extending between opposing spar caps. The skin, typically manufactured from layers of fiber composite and a lightweight core material, forms the exterior aerodynamic airfoil shape of the rotor blade. Further, the spar caps provide increased rotor blade strength by integrating one or more structural elements running along the length of the rotor blade on both interior sides of the rotor blade. The shear web(s) includes structural beam-like components running essentially perpendicular between the top and bottom spar caps and extend across the interior portion of the rotor blade between the outer skins. The spar caps have typically been constructed from glass fiber reinforced composites, though some larger blades may include spar caps constructed from carbon fiber reinforced composites.
The size, shape, and weight of rotor blades are factors that contribute to energy efficiencies of wind turbines. An increase in rotor blade size increases the energy production of a wind turbine, while a decrease in weight also furthers the efficiency of a wind turbine. Furthermore, as the size of wind turbines increases, particularly the size of the rotor blades, so do the respective costs of manufacturing, transporting, and assembly of the wind turbines. The economic benefits of increased wind turbine sizes must be weighed against these factors.
One known strategy for reducing the costs of pre-forming, transporting, and erecting wind turbines having rotor blades of increasing sizes is to manufacture the rotor blades in blade segments. The blade segments may be assembled to form the rotor blade after, for example, the individual blade segments are transported to an erection location. For example, some rotor blades include either bonded or bolted joints. One such bolted joint includes a chord-wise extending pin securing a male shear web member or spar member within a female shear web member so as to join adjacent blade segments.
However, certain issues are associated with the chord-wise extending pin. For example, the edge loading of the joint without pin contact is indefinite. Further, the chord-wise extending pin and any other pins needed to secure the joint together, however, may require bushings. During operation of the wind turbine, such bushings may experience walk-out from its bore hole, thereby causing the joint to become loosened over time.
Thus, there is a need for a joint assembly for a segmented rotor blade that addresses the aforementioned issued. Accordingly, the present disclosure is directed to a joint assembly for wind turbine rotor blades having flanged bushings.